Exo-S-mecamylamine formulation and use in treatment

ABSTRACT

A pharmaceutical composition includes a therapeutically effective amount of exo-S-mecamylamine or a pharmaceutically acceptable salt thereof, substantially free of exo-R-mecamylamine in combination with a pharmaceutically acceptable carrier. Preferably the amount is about 0.5 mg to about 20 mg. Medical conditions are treated by administering a therapeutically effective amount of exo-S-mecamylamine or a pharmaceutically acceptable salt thereof, substantially free of its exo-R-mecamylamine, said amount being sufficient to ameliorate the medical condition. The medical conditions include but are not limited to substance addiction (involving nicotine, cocaine, alcohol, amphetamine, opiate, other psychostimulant and a combination thereof), aiding smoking cessation, treating weight gain associated with smoking cessation, hypertension, hypertensive crisis, Tourette&#39;s Syndrome and other tremors, cancer (such as small cell lung cancer), atherogenic profile, neuropsychiatric disorders (such as bipolar disorder, depression, an anxiety disorder, schizophrenia, a seizure disorder, Parkinson&#39;s disease and attention deficit hyperactivity disorder), chronic fatigue syndrome, Crohn&#39;s disease, autonomic dysreflexia, and spasmogenic intestinal disorders.

CROSS-REFERENCETO RELATED APPLICATIONS

This application is a continuation of Ser. No. 12/886,887, filed Sep.21, 2010, which is a continuation of Ser. No. 12/651,813, filed Jan. 4,2010, now U.S. Pat. No. 8,026,283 issued Sep. 27, 2011, which is acontinuation of Ser. No. 11/278,770, filed Apr. 5, 2006, which is acontinuation of Ser. No. 10/441,947, filed May 19, 2003, now U.S. Pat.No. 7,101,916 issued Sep. 5, 2006, which is a continuation of Ser. No.09/882,935, filed Jun. 15, 2001, now U.S. Pat. No. 6,734,215 issued May11, 2004, which is a continuation-in-part of PCT/US99/30153, filed Dec.16, 1999, and takes the benefit of U.S. Provisional Application No.60/112,534, filed Dec. 16, 1998.

BACKGROUND

(1) Field of the Invention

The present invention is in the field of chemical synthesis ofstereoisomers and more particularly the exo-S-mecamylamine stereoisomerand the use of exo-S-mecamylamine in medical treatments.

(2) Description of Related Art

Mecamylamine (N,2,3,3-tetramethylbicyclo-[2.1.1]heptan-2-aminehydrochloride, 826-39-1) was developed and characterized by Merck & Co.,Inc., as a ganglionic blocker with clinically significant hypotensiveactions (Stone et al., J Med Pharm Chem 5(4):665-90, 1962). Uniquecharacteristics of mecamylamine—including exceptional oral efficacy,rapid onset, long duration of action, and nearly complete absorptionfrom the gastrointestinal tract—made mecamylamine at that time moredesirable than the existing ganglionic blockers (Baer et al., Am JPhysiol 186:180-6, 1956).

Despite mecamylamine's proven efficacy in the treatment of hypertension,its side effects resulting from broad parasympathetic inhibition led toits demise as a first line treatment for essential hypertension.Generalized ganglionic blockade may result in atony of the bladder andgastrointestinal tract impaired sexual function, cycloplegia,xerostomia, diminished perspiration and postural hypotension. Amongmecamylamine side effects experienced at the antihypertensive dose of 25mg/day were cardiovascular effects, hypothermia, tremors, anti-diuresis,antinociception, blurred vision, impotency, dysuria, tremor, choreiformmovements, mental aberrations, nervousness, depression, anxiety,insomnia, slurred speech, weakness, fatigue, sedation, headache,constipation and renal insufficiency. Even at lower doses, such as 7.5mg/day, some evidence for constipation has been reported. Minorincreases in taste perversion (altered sense of taste), dizziness,insomnia and dyspepsia were noted. Mecamylamine continued to be used inspecial situations, such as hypertensive encephalopathy (Moser, 1969),hypertensive crises, and autonomic dysreflexia (Braddom and Johnson,1969; Braddom and Rocco, 1991). Outside of a few laboratories and anoccasional clinical study, sales of mecamylamine are rare.

In addition to its peripheral ganglionic blocking actions, mecamylaminecrosses the blood brain barrier and functions as a selective nicotinicreceptor antagonist at doses which do not have a significant effect onparasympathetic function (Banerjee et al., Biochem Pharmacol 40:2105-10,1990; Martin et al., Med Chem Res 2:564-77, 1993). As a result,mecamylamine blocks most of the physiological, behavioral, andreinforcing effects of tobacco and nicotine (Martin et al., BiochemPharmacol 38:3391-7, 1989). In studies of nicotine dependence, doses of2.5 to 20 mg have been administered acutely to human subjects. Forexample, Rose et al. (1989) found that low doses of mecamylamine (2.5 to10 mg), which were well tolerated, reduced the subjective effects ofsmoking in adult smokers.

In a recent double blind placebo-controlled study investigating thebenefits of oral mecamylamine (5 mg/day b.i.d.) in adults for smokingcessation treatment, there was no significant increase over controls inadverse effects reported with mecamylamine treatment for most symptoms,including blurred vision, dizziness when standing, dry mouth, weakness,abdominal pains, or difficult urination. The most prevalent symptom withthe mecamylamine treatment was mild constipation; at some point duringthe five weeks of mecamylamine treatment, 70% of the subjects reportedthat symptom versus 32% in the placebo group (Rose et al., 1994).Mecamylamine also has been reported to alter cognitive functioning(Newhouse P A et al, Neuropsychopharmacology 10:93-107, 1994),electrical brain waves (Pickworth W B, Herning R I, Henningfield J E,Pharmacology Biochemistry & Behavior 30:149-153, 1988) and corticalblood flow (Gitalman D R, Prohovnik I, Neurobiology of Aging 13:313-318,1992).

While most animal studies used more than 0.5 mg/kg, Driscoll found thata small dose of only mecamylamine (<0.3 mg/kg, not 0.5 mg/kg) tohigh-avoidance rats increased their avoidance success almost as much as0.1 mg/kg nicotine (but less than 0.2 mg/kg nicotine). Based on hisexperiments, Driscoll concluded: “mecamylamine may exert unpredictableeffects on rats at the dosage levels used to block nicotine inbehavioral tests” (Driscoll P., Psychopharmacologia (Berl.) 46:119-21,1976).

Many organic compounds exist in optically active forms, i.e., they havethe ability to rotate the plane of polarized light. In describing anoptically active compound, the prefixes R and S are used to denote theabsolute configuration of the molecule about its chiral center(s). Theprefixes (+) and (−) or d and l are employed to designate the sign ofrotation of polarized light by the compound, with (−) and l meaning thatthe compound is levorotatory. A compound prefixed with (+) and d isdextrorotatory. For a given chemical structure, these compounds, calledstereoisomers, are identical except that they are mirror images of oneanother. A specific stereoisomer may also be referred to as anenantiomer, and a mixture of such isomers is often called anenantiomeric or racemic mixture.

Stereochemical purity is of importance in the field of pharmaceuticals,where 12 of the 20 most prescribed drugs are optically active. Oneexample is the l-form of propranolol, which is about 100 times morepotent than the d-form. Optical purity is important since certainisomers may be deleterious rather than simply inert. Another example isd-thalidomide that appears to be a safe and effective sedative forcontrolling morning sickness during pregnancy; whereas, l-thalidomide isthought to be a potent teratogen.

Mecamylamine has been marketed as a racemic mixture comprising theoptical isomers exo-S-mecamylamine and exo-R-mecamylamine hydrochloride.Previous studies aimed at investigating the pharmacology of these twoisomers have generally found little or no difference in potency orefficacy. For example, Stone et al. (1962) compared the effects of(+)-mecamylamine hydrochloride with racemic mecamylamine hydrochlorideon nicotine-induced convulsions and pupil dilation and found essentiallyno significant differences between the two compounds and concluded that“optical isomerism does not play a significant role in determining thedegree of activity.” (Stone, supra, p. 675). Schonenberger et al. (HelvChim Acta 69:283-7, 1986) reported “interesting differences” in theactions of d- and l-mecamylamine hydrochloride in assays measuringneuromuscular transmission. However, they provided no details on thedifferences.

In U.S. Pat. No. 5,039,801, Brossi and Schonenberger disclosed that “theantipodes (−)- and (+)-mecamylamine were obtained here from thecorresponding methylbenzylureas in 40% yield each and were of highoptical purity (95%, HPLC), affording hydrochloride salts which wereoptically pure after one crystallization.” (col. 3, lines 32-37).However, in disclosing their experimental findings, they mention thatthe “etheral extract of the concentrated, acidified reaction mixture wasconcentrated and the residue distilled (Kugel, 180°, 20 torr) to give6.08 g (96%) (−)-12 as a tlc. pure colorless liquid which turned to awaxy solid on standing in cold: [α]_(D)=77.0° (c+2.6 in benzene) lit.(+)-12: [α]_(D)=+80.1° (c=3 in benzene). The combined org extracts fromthe alkaline aqueous phase were concentrated, the resulting liquid wasmixed with 20 ml Et₂O and crude hydrochloride (+)-1.HCl was precipitatedby addition of a slight excess of HCl in Et₂O. After filtration, thefinely powdered colorless solid was recrystallized from 2-propanol togive 1.02 g (64%) (+)-1.HCl as needles [α]_(D) +20.1° (c+1.7 in CHCl₃).The more polar urea 3 (1.85 g, 5.89 mmol) was treated in exactly thesame manner to give 752 mg (63% (−)-1.HCl as colorless needles: [α]_(D)−20.0° (c=2.2 in CHCl₃).” Col. 6, lines 20-37. However, no in vitro orin vivo data were disclosed.

Suchocki et al. (J Med Chem 34:1003-10, 1991) investigated the actionsof d- and l-mecamylamine hydrochloride in assays measuringnicotine-induced depression of spontaneous locomotor activity andantinociception. They found that both optical isomers had similarpotency in blocking the antinociception caused by nicotine; whereas, thepotency of the (+)-mecamylamine isomer in blocking the nicotine-induceddepression of spontaneous locomotor activity was unable to be determineddue to an experimental confound.

Tourette's Syndrome (TS) is an autosomal dominant neuropsychiatricdisorder characterized by a range of symptoms, including multiple motorand phonic tics. It is a hyperkinetic movement disorder expressedlargely by sudden, rapid, brief, recurrent, nonrhythmic, stereotypedmotor movements (motor tics) or sounds (phonic tics), experienced asirresistible impulses but which can be suppressed for varying lengths oftime (Tourette Syndrome Classification Study Group, Arch Neurol50:1013-16). Motor tics generally include eye blinking, head jerking,shoulder shrugging and facial grimacing, while phonic or vocal ticsinclude throat clearing, sniffling, yelping, tongue clicking andcoprolalia. The symptoms typically begin in childhood and range fromrelatively mild to very severe over the course of a patient's lifetime(Robertson M M, Br J Psychiatry, 154:147-169, 1989). Many TS patientsalso exhibit other neuropsychiatric abnormalities including obsessivecompulsive symptoms (Pauls D L et al. Psychopharm Bull, 22:730-733,1986), hyperactivity and attention deficit (Comings Del., Himes J A,Comings B G, J Clin Psychiatry, 51:463-469, 1990). Problems with extremetemper or aggressive behavior also are frequent (Riddle Mass. et al.Wiley Series in Child and Adolescent Mental Health, Eds. Cohen D J,Bruun, R D, Leckman J F, New York City, John Wiley and Sons, pp.151-162, 1988; Stelf M E, Bornstein R A, Hammond L, A survey of TouretteSyndrome patients and their families: the 1987 Ohio Tourette Survey,Cincinnati, Ohio Tourette Syndrome Association, 1988), as are schoolrefusal and learning disabilities (Harris D, Silver A A, LearningDisabilities, 6(1): 1-7, 1995; Silver A A, Hagin R A, Disorders ofLearning Childhood, Noshpitz J D, ed. New York City Wiley, pp. 469-508,1990).

While the pathogenesis of TS is still unknown, excessive striataldopamine and/or dopamine receptor hypersensitivity has been proposed(Singer H S et al. Ann Neurol, 12:361-366, 1982), based largely on thetherapeutic effectiveness of dopamine receptor antagonists. TS isfrequently treated with the dopamine antagonist haloperidol (Haldol®,Ortho-McNeil Pharmaceutical, Raritan, N.J.), which is effective in about70% of cases (Erenberg G, Cruse R P, Rothner, A D, Ann Neurol,22:383-385, 1987; Shapiro A K, Shapiro E, Wiley series in child andadolescent mental health, Eds. Cohen D J, Bruun R D, Leckman J F, NewYork City, John Wiley and Sons, pp. 267-280, 1988). Other neurolepticsinclude pimozide (Shapiro E S et al. Arch Gen Psychiatry, 46:722-730,1989), fluphenazine (Singer H S, Gammon K, Quaskey S. PediatNeuroscience, 12:71-74, 1985-1986), and risperidone (Stamenkovic et al.,Lancet 344:1577-78, 1994). The α-adrenergic agonist clonidine, whichalso is effective for associated attention deficit hyperactivitydisorder (ADHD), has only a 40% success rate for motor and vocal tics(Brunn R D, J Am Acad Child Psychiatry, 23:126-133, 1984; Cohen D J etal. Arch Gen Psychiatry 37:1350-1357, 1980). Other medications withvarying degrees of effectiveness include clonazepam (Gonce M, Barbeau A.Can J Neurol Sci 4:279-283, 1977), naloxone (Davidson P W et al. ApplRes Ment Retardation 4:1-4, 1983) and fluoxetine (Riddle M A et al. J AmAcad Child Adol Psychiatry 29:45-48, 1990). A commonly used medicationis haloperidol (Erenberg G, Cruse R P, Rothner A D, Ann Neurol,22:383-385, 1987). However, therapeutic doses of haloperidol frequentlycause difficulty in concentration, drowsiness, depression, weight gain,parkinsonian-like symptoms—and with long-term use—tardive dyskenesia(Shapiro A K, Shapiro E, Tourette's Syndrome and Tic Disorders: ClinicalUnderstanding and Treatment. Wiley series in child and adolescent mentalhealth. Eds. Cohen, D J, Bruun, R D, Leckman J F, New York City, JohnWiley and Sons, pp. 267-298, 1988). The side effect of tardivedyskinesia is particularly bothersome because it may add additionalabnormal, involuntary movements of the tongue, jaw, trunk and/orextremities.

Erenberg et al. (Erenberg G, Cruse R P, Rothner A D, Ann Neurol22:383-385, 1987) found that most patients with TS stop using theirhaloperidol or other neuroleptic medications by age 16, often because ofside effects. After TS patients quit medication, they have less controlover speech and movement, which disqualify many for full-time,responsible jobs. The public, including law enforcement officers, oftenidentify the symptoms as intoxication. Unexpected movements andcoprolalia cause great social difficulties.

It has been observed that 50% of children presenting with TS also haveAttention Deficit Hyperactivity disorder (ADHD). ADHD is aneurobiological disorder characterized by impaired attentiveness,increased impulsivity, and hyperactivity. ADHD is now the most commonlydiagnosed childhood psychiatric condition, with some 3.5 millionafflicted. In addition, 60% of adolescents with ADHD continue to havesymptoms in adulthood, representing another 2.5 million patients.

Many neuropsychiatric disorders involve abnormal or involuntarymovements including but not limited to obsessive-compulsive disorder(OCD), TS, ADHD, hemidystonia, and chorea, such as Huntington's chorea.These diseases may be caused by neurochemical imbalances in the brain'sbasal ganglia. Acetylcholine, by activating nAChrs in the basal ganglia,regulates motor activity in humans (Clarke PBS, Pert A, Brain Res348:355-358, 1985). Nicotinic stimulation excites activity in thedopamine (DA)-producing cells in the basal ganglia (Clarke PBS et al, JPharmacol Exper Therapeutics 246:701-708, 1988; Grenhoff J, Aston-JonesG, Svennson T H, Acta Physiol Scand 128:351-358, 1986; lmperato A, MulasA, Di Chiara G, Eur J Pharmacol 132:337-338, 1986), while mecamylamineblocks nAChr and inhibits DA release from basal ganglia structures(Ahtee L, Kaakkola S, Br J Pharmacol 62:213-218, 1978).

U.S. Pat. No. 5,574,052 to Rose and Levin discloses agonist-antagonistcombinations to reduce the use of nicotine and other drugs. Incombination with nicotine, the nicotinic antagonist mecamylamine wasgiven to treat tobacco dependency. Rose and Levin proposed includingboth nicotine and mecamylamine in a patch. Rose and Levin also suggestedthat such agonist-antagonist combinations could be used in otherpsychopathological disorders and cases involving neuronal dysfunction(e.g., manic depression, schizophrenia and hypertension due tosympathetic autonomic disorder).

It would benefit patients to be able to have better symptom control andfewer side effects. Our clinical experience with mecamylamine racematein human patients with a variety of disorders supports a variety ofuses. Herein is disclosed improved symptom control with isomerexo-S-mecamylamine for the treatment of a variety of nicotine-responsiveneuropsychiatric disorders.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide improved therapy forpatients with nicotine-responsive neuropsychiatric disorders.

It is a further object of the present invention to provide therapy withfewer side effects to improve patient medication compliance, as well asto improve their quality of life and social functioning.

In one embodiment, there is provided a pharmaceutical composition thatincludes a therapeutically effective amount of exo-S-mecamylamine or apharmaceutically acceptable salt thereof, substantially free ofexo-R-mecamylamine in combination with a pharmaceutically acceptablecarrier. Preferably the amount is about 0.5 mg to about 1000 mg. Thepreferred composition contains exo-S-mecamylamine hydrochloride and apharmaceutically acceptable carrier. The pharmaceutical composition ofclaim 1 can be adapted for oral, intrathecal, transdermal, implantableand/or intravenous administration. The pharmaceutical can be atransdermal patch, solid preparation, or a sustained release form.Preferably, the substantially pure exo-S-mecamylamine is greater than95% by weight and exo-R-mecamylamine is less than 5% by weight. Morepreferably, the substantially pure exo-S-mecamylamine is greater than98% by weight and exo-R-mecamylamine is less than 2% by weight. Morepreferably, the substantially pure exo-S-mecamylamine is greater thangreater than 99% by weight and exo-R-mecamylamine is less than 1% byweight. Even more preferably, the substantially pure exo-S-mecamylamineis greater than 99.5% by weight and exo-R-mecamylamine is less than 0.5%by weight. Most preferably, the substantially pure exo-s-mecamylamine isgreater than 99.7% by weight and exo-R-mecamylamine is less than 0.3% byweight.

In other embodiments, there are provided treatments of medicalconditions by administering a therapeutically effective amount ofexo-S-mecamylamine or a pharmaceutically acceptable salt thereof,substantially free of its exo-R-mecamylamine, said amount beingsufficient to ameliorate the medical condition. Preferably, the methodprovides for administering exo-S-mecamylamine intravenously,intramuscularly, transdermally, intrathecally, orally or by bolusinjection. Preferably, the dosage of exo-S-mecamylamine is about 0.5 mgto about 1000 mg, depending on dosage form and its expected life.Preferably, exo-S-mecamylamine is administered one to four times perday. The medical conditions include but are not limited to substanceaddiction (involving nicotine, cocaine, alcohol, amphetamine, opiate,other psychostimulant and a combination thereof), aiding smokingcessation, treating weight gain associated with smoking cessation,hypertension, hypertensive crisis, herpes type I and II, Tourette'sSyndrome and other tremors, cancer (such as small cell lung cancer),atherogenic profile, neuropsychiatric disorders (such as bipolardisorder, depression, anxiety disorder, panic disorder, schizophrenia,seizure disorders, Parkinson's disease and attention deficithyperactivity disorder), chronic fatigue syndrome, Crohn's disease,autonomic dysreflexia, and spasmogenic intestinal disorders.

BRIEF DESCRIPTION OF THE DRAWING(S)

FIG. 1 is a gas chromatograph printout showing that exo-S-mecamylamineelutes purely at 63.971 minutes after placement on the column.

FIG. 2 shows the structures of mecamylamine generally (+/−).

FIG. 3 is a bar graph showing total distance traveled in 60 minutes byrats having undergone seven days of sensitization with saline ormecamylamine at one of 3 doses. The dagger symbol indicates significantdifferences from the Saline/Saline control group. The asteriskidentifies significant differences from the Saline/Nicotine controlgroup.

FIG. 4 is a bar graph showing the center distance traveled by rats inthe same study.

FIG. 5 is a bar graph showing the vertical activity of rats in the samestudy.

FIGS. 6A-6D are bar graphs showing the percentage of rats that seized(6A), latency to seizure (6B), duration of seizure (6C), and severity ofseizures in rats treated with saline or various doses of mecamylamineand its stereoisomers followed by nicotine (3.6 mg/kg).

FIG. 7 is a bar graph illustrating the mean total distance traveled incentimeters in rats receiving any of saline or 10 mg/kg mecamylamine orits stereoisomer.

DETAILED DESCRIPTION OF THE INVENTION

Although there is some variability from one patient to another, it isgenerally observed that, by administering an effective amount of onlyexo-S-mecamylamine, it is possible to accomplish a more “targeted”therapy, which provides the desired effect without the consequences ofall the other pharmacologic effects. This is important since it is notdesirable for all patients to be administered a compound with such amultifaceted spectrum of activity.

Synthesis of mecamylamine has been disclosed in three patents: U.S. Pat.No. 2,831,027 (1958), U.S. Pat. No. 2,885,428 (1959) and U.S. Pat. No.5,986,142 (1999).

For the synthesis of mecamylamine one starting material is camphene, theracemate or either isomer. The isomers are available from naturalsources or can be obtained by resolution using liquid chromatographyusing a chiral medium (Armstrong, J Chrom A, 666:445, 1994). They canalso be made using kinetic resolution wherein a chiral reagentselectively reacts with one isomer leaving the other intact (Jenke, JOrganomet Chem, 405:383, 1991). The camphene isomers can also be madefrom chiral precursors (Hana, Chem Ber, 111:2527, 1978).

Camphene, racemic or isomeric, in an acidic medium can be reacted with anitrogen source, such as azide (Pancrazi, Bull Chim Soc (Fr.), (1977)162), cyanide (Stein, J Am Chem Soc, 78:1514, 1956; Stone, J Med PharmChem, 5:665, 1962; Pfister, U.S. Pat. No. 2,831,027 (1958)) orthiocyanate (Luskin, U.S. Pat. No. 2,885,428; CA. 53:20124h). Theintermediates so produced can be converted to mecamylamine, the racemateor either isomer.

Camphene, racemic or isomeric, can be converted to camphenehydrochloride (Geam, Aust J Chem, 27:567, 1974) which can be reactedwith nitrite (Huckel, Ann 528 (1937) 57; CA. 31:3033-4) to produce anintermediate which can be converted to mecamylamine, the racemate oreither isomer. The hydrochloride can also be reacted with an amine toyield mecamylamine, racemic or isomeric (Stone, J Med Pharm Chem, 5:665,1962), or an intermediate that can be converted to mecamylamine, racemicor either isomer.

Camphenilone, racemic or as either of its isomers, can be reacted with amethyl lithium or similar nucleophilic methyl to give an alcohol (Stone,J Med Pharm Chem, 5:665, 1962; Gream, Aust J Chem, 27 (1974) 567). Thealcohol or its derivatives can be subjected to the acidic reactionsdescribed above for camphene to yield mecamylamine, racemic or as eitherof its isomers, or products that can be converted to it (Stone, J MedPharm Chem 5:665, 1962). A similar alcohol can be made from camphene,racemic or isomeric (Coxon, Tetrahedron, 26:3755, 1970) and subjected tothe same reactions yielding similar products.

The reaction of organic azides with camphene, racemic or as either ofits isomers followed by either photolytic or thermal decomposition(Huisgen, Chem Ber, 98:3992, 1965; Franz, J Org Chem, 29:2922, 1964) ofthe reaction product yields an aziridine which can be ring opened (Gold,J Org Chem, 37:2208, 1972) and transformed into mecamylamine, theracemate or either isomer.

Mecamylamine can be synthesized in either the racemic form or theisomers. The racemic product can be resolved into its isomers by saltformation using chiral acids (carboxylic, sulphonic, phosphoric(Pfister, U.S. Pat. No. 2,831,027 (1958); Stone, J Med Pharm Chem,5:665, 1962) and then the isomer regenerated, by derivatization withchiral molecules. The resulting diastereomers can be separated bycrystallization or by simple chromatography (Schonenberger, Helv. Chim.Acta., 69 (1986) 283), and then the stereoisomer regenerated, or byliquid chromatography using a chiral medium.

Definitions:

“exo-S-Mecamylamine” includes the +-stereoisomer ofN,2,3,3-tetramethylbicyclo-[2.1.1]heptan-2-amine hydrochloride,826-39-1. This stereoisomer is also referred to asexo-S-N,2,3,3-tetramethyl-bicycl-o-[2.1.1]heptan-2-amine hydrochloride.It has positive optical rotation. “exo-R-mecamylamine” is the(−)-stereoisomer.

“Related exo-S-mecamylamine compounds” include various activestereoisomers and substituted analogs of mecamylamine (Stone et al., JMed Pharm Chem 5(4):665-90, 1962, hereby incorporated by reference).Activity can be tested in rats by nicotine convulsions, pupil dilatationand by other methods such as those described below. Such activity wasroutinely lost with larger substitutions for the methyl groups, whichare not a part of this invention. Both methyl or dimethyl groups on theamino group were more active than other substituents and are includedherein. The d form was active; however, the dl racemate appeared to beslightly more active. Consequently the l form seems to have significantactivity. Stone et al. reported that the exo form (methylamino grouplies on the same plane as the methylene bridge) was always stronger thanthe endo form (methylamino group lies below the methylene bridge andtends to lie within the cage created by the bridge). In addition, apartial structure, 2,2,-dimethyl-3-methylaminobutane, also was active.Stone concluded that the slight differences in activity betweendifferent models for the d form and other analogs was not significant.

The term “substantially free of the exo-R-mecamylamine hydrochloride” asused herein means that the composition contains at least about 95% byweight of exo-S-mecamylamine and less than about 5% by weight ofexo-R-mecamylamine. In a more preferred embodiment, the compositioncontains at least 98% by weight of exo-S-mecamylamine and less thanabout 2% by weight of exo-R-mecamylamine. In the most preferredembodiment, the composition contains at least 99% by weight ofexo-S-mecamylamine and less than about 1% by weight ofexo-R-mecamylamine.

“Beneficial effect” is a noticeable improvement over the baselineclinically observable signs and symptoms and may include subjectivepatient reports of improvement. For example, a beneficial effect inmotor disorders includes decreases in tic frequency or severity, butimprovements also can be manifested indirectly through reductions inanxiety, aggressive outbursts, and premonitory urges that often precedeor compound the severity of abnormal movements. Treatment effects can bequantified by clinical observations and videotape scoring. Beneficialeffects can also be predicted by the results of animal screening. Forexample, Suemaru et al (ibid) has proposed that the nicotine-inducedrat-tail tremor can be used to screen for compounds to treat tremors.Repeated nicotine administration can induce locomotor hyperactivity anda tail tremor in rats which is blocked with mecamylamine (0.1-1 mg/day,ip) but not by hexamethonium which does not readily enter the brain.(Suemaru K., Oishi R, Gomita Y, Arch Pharm 350:153-57, 1994).

The Yale Global Tic Severity Scale (YGTTS) is the most widely usedclinical assessment rating scale used to assess tic symptoms. Itprovides an objective measure of tic frequency of severity based onclinical observations. This scale includes a tic symptom inventory,which is filled out based on the patient's personal recall of ticsoccurring over the previous week. Using this inventory as a guide, theclinician then rates the severity of both motor and vocal tics on fiveseparate dimensions: number, frequency, intensity, complexity, andinterference. In addition, there is also a separate rating of globalimpairment, which characterizes the impact of the disorder on thepatient's social function, self-esteem, etc., over the previous week.There are numerous rating systems that can be substituted therefore.

An objective method for rating tic symptoms employs video recording ofpatients. A videotape of at least five minutes is viewed and thefrequency and severity of both motor and vocal tics are recorded. Videotaping has proven a valuable adjunct to clinical rating systems for drugtrials (Leckman J F, et al., Arch Gen Psychiatry, 48:324-328, 1991;Shapiro E S, et al., Arch Gen Psychiatry, 46:722-730, 1989; McConville BJ, Fogelson M H, Norman A B, Klykylo W M, Manderscheid M A, Parker K W,Sanberg P R, Am J Psychiatry, 148:793-794, 1991; Silver A A, Shytle R D,Philipp M K, Sanberg P R, The Effects of Nicotine on Biological SystemsII. PBS Clarke, M. Quik and K. Thurau, (Eds.); Advances inPharmacological Sciences, Birkhauser Publishers, pp. 293-299, 1995;Reveley M A, et al., Journal of Psychopharmacology Supplement, A30, 117,1994).

Beneficial effects in obsessive compulsive disorders include diminutionin the obsessive or compulsive behavior, which can be confirmed bypatient or family reports or psychiatric assessment. Beneficial effectsin nicotine, alcohol or cocaine abuse include longer drug-free periodsas well as subjective feelings of less need for the drug. Beneficialeffects in herpes infections include aborting outbreaks, faster healingand longer infection-free period.

“Side effects” are unwanted actions which may include but are notlimited to cardiovascular effects, hypothermia, tremors, anti-diuresis,antinociception, blurred vision, impotency, dysuria, tremor, choreiformmovements, mental aberrations, nervousness, depression, anxiety,insomnia, slurred speech, weakness, fatigue, sedation, headache,constipation, renal insufficiency, taste perversion (altered sense oftaste), dizziness, and dyspepsia.

The term “effective amount” refers to the amount of exo-S-mecamylaminethat is necessary to provide benefit. The precise amount required willvary depending upon the age and weight of the subject, severity of thedisorder, route of administration, and so forth, but may easily bedetermined by routine experimentation, as described below in theclinical examples. In general, however, an effective amount ofexo-S-mecamylamine range from about 0.001 mg/kg to about 6 mg/kg perday, preferably about 0.002 mg/kg to about 3 mg/kg, more preferablyabout 0.005 mg/kg to about 2 mg/kg, and most preferably about 0.01 toabout 1.5 mg/kg. A starting dose for adults with drug-resistant TS isabout 2.5 mg per day, with dosage adjusted according to return ofsymptoms. A small child with mild ADHD preferably starts with 1 mg perday or less.

The term “pharmaceutically acceptable” refers to a lack of unacceptabletoxicity in a compound, such as a salt or excipient. Pharmaceuticallyacceptable salts combine inorganic anions such as chloride, bromide,iodide, sulfate, sulfite, nitrate, nitrite, phosphate, and the like, andorganic anions such as acetate, malonate, pyruvate, propionate,cinnamate, tosylate, mesylate, citrate, and the like Pharmaceuticallyacceptable excipients are described at length by E. W. Martin, inRemington's Pharmaceutical Sciences (Mack Publishing Co.).

Pharmaceutical compositions containing exo-S-mecamylamine may containone or more pharmaceutical carriers. The term “pharmaceuticallyacceptable carrier” refers to any generally acceptable excipient that isrelatively inert, non-toxic and non-irritating. When the carrier servesas a diluent, it may be solid, semisolid, or liquid material acting as avehicle, excipient, or medium for the active ingredient. Pharmaceuticalunit dosage forms may be prepared for administration by any of severalroutes, including, but not limited to, oral and parenteral (especiallyby intramuscular and intravenous injection, or by intrathecal,subcutaneous implant or transdermal administration). Representative ofsuch forms are tablets, soft and hard gelatin capsules, powders,lozenges, chewing gums, emulsions, suspensions, syrups, solutions,sterile injectable solutions, and sterile packaged powders. Compositionscontaining nicotine antagonists may be formulated by procedures known inthe art so as to provide rapid, sustained, or delayed release of any orall of the compounds after administration. In addition to the commondosage forms set out above, the compounds of the present invention mayalso be administered by controlled release means and/or delivery devicessuch as those described in U.S. Pat. Nos. 3,845,770; 3,916,899;3,536,809; 3,598,123; 4,008,719; 5,910,321; 5,348,746; and the like bythe various manufacturers of controlled release means and/or deliverydevices.

As the exo-S-mecamylamine formulation of the present invention is wellsuited to oral administration, preferred carriers facilitate formulationin tablet or capsule form. Solid pharmaceutical excipients such asmagnesium stearate, calcium carbonate, silica, starch, sucrose,dextrose, polyethylene glycol (PEG), talc, and the like may be used withother conventional pharmaceutical adjuvants including fillers,lubricants, wetting agents, preserving agents, disintegrating agents,flavoring agents, and binders such as gelatin, gum arabic, cellulose,methylcellulose, and the like, to form admixtures which may be used assuch or may be tabulated, encapsulated, or prepared in other suitableforms as noted above. A general description of formulation is given inRemington's Pharmaceutical Sciences (Mack Publishing Co.).

Modes of Administration

Administration is preferably by oral dosage but may be by transdermalapplication, intranasal spray, bronchial inhalation, suppository,parenteral injection (e.g., intramuscular or intravenous injection), andthe like. Carriers for parenteral administration include, withoutlimitation, aqueous solutions of dextrose, mannitol, mannose, sorbitol,saline and other electrolyte solutions, pure water, ethanol, glycerol,propylene glycol, peanut oil, sesame oil,polyoxyethylene-polyoxypropylene block polymers, and the like. One mayadditionally include suitable preservatives, stabilizers, antioxidants,antimicrobials and buffering agents, for example, BHA, BHT, citric acid,ascorbic acid, tetracycline, and the like. Alternatively, one mayincorporate or encapsulate the nicotine antagonist formulation in asuitable polymer matrix or membrane, thus providing a sustained-releasedelivery device suitable for implantation or application to the skin.Other devices include indwelling catheters and devices such as theAlzet® minipump.

The invention has been disclosed by direct description. The followingare examples showing the efficacy of the method in providing benefit.The examples are only examples and should not be taken in any way aslimiting to the scope of the method.

Analysis of Exo-S-Mecamylamine Hydrochloride

Mecamylamine hydrochloride (Lot 2351) was 99.95% pure by gaschromatograph, as shown in FIG. 1. The gas chromatograph retainedexo-S-mecamylamine hydrochloride for 63.971 minutes, and no othersignificant peaks were observed. The chloride content was 17.2%.Considering that chloride comprises 17.4% of the mass of mecamylaminehydrochloride, this indicates a high level of purity. No camphene orother impurities were detected. Optical rotation was +19.4°. This lotwas used in Examples 1 and 9 below. The structures of mecamylamine andthe stereoisomers are shown in FIG. 2.

Pharmacology

General Methods

Animals

Male Sprague-Dawley rats (Zici-Miller Laboratories, Allison Park, Pa.)weighing an average of 463 grams were used. They were housed in groupsof 2-4 per cage, allowed free access to food and water, and maintainedon a reverse 12 h light/12 h dark lighting cycle, with night being 8:00AM through 8:00 PM. All testing occurred during the rats' nocturnalcycle.

Measurements and Apparatus

For all locomotor testing, a Digiscan Animal Activity Monitors (ModelRXYSCM, Accusan, Inc., Columbus, Ohio) was used. Box dimensions were 42cm×42 cm×30 cm, and the walls and floors were clear acrylic. Each boxused in this study had photocells that, when the light beam was brokenby the rat's movement, calculate a number of variables. All locomotoractivity was automatically captured and recorded with a Digipro softwareprogram.

To assess catalepsy (the ability to maintain position after being placedtherein) induced by haloperidol and blocked with treatment, the bar testwas used. The bar was placed 9 cm above the tabletop. The rat's forepawswere simultaneously placed on the bar and the hind paws placed under therat for support. Time was measured from the second both forepaws wereplaced on the bar until the rat removed both paws from the bar. Theminimum time was 1 second, and the maximum time allowed was 60 seconds.The shorter the time on the bar, the greater the blockage ofhaloperidol-induced catalepsy.

Drugs

Mecamylamine HCl was obtained from Layton Bioscience, Inc., Atherton,Calif. Optical isomers of mecamylamine were resolved from the racemateaccording to procedures reported by Stone et al (supra), but withsignificant modifications to improve optical purity and yields (seeabove). (−)-Nicotine was obtained from Sigma Chemical Co. (St. Louis,Mo.). Haloperidol lactate (Solopak®) was obtained from a local pharmacy.All drugs were dissolved in saline at a volume of 1 mg/ml and injectedsubcutaneously.

EXAMPLE 1

Eighty-eight experimentally naive adult male Sprague-Dawley derived ratswere housed two per cage and allowed free access to food and water. Eachrat received a randomly assigned pretreatment condition for sevenconsecutive days. On each day of this pretreatment period, rats receivedan injection of saline, racemic mecamylamine, exo-R-mecamylamine, orexo-S-mecamylamine 20 minutes prior to receiving a second injection ofeither saline or nicotine (0.4 mg/kg s.c.) and left in their home cage.Pretreatment assignment was arranged so that 2 rats from each conditionwere started and tested together to control for sequence effects. Ratsreceived no treatment or testing on the day 8. On day 9, rats weretested for the presence of the sensitized locomotor stimulant responseto nicotine. Each rat was placed into a locomotor box for a 60 minutehabituation period, followed by an injection of nicotine (0.4 mg/kgs.c.), and then placed immediately back into the locomotor box. Acomputer recorded data over the next 60 minutes at 5-minute intervals.

FIGS. 3-5 illustrate 3 dependent variables respectively for all groupsfollowing a test injection of 0.4 mg/kg nicotine on day 9. Thesaline/nicotine (sal/nic) pretreatment group exhibited a sensitizedlocomotor response to nicotine, which was not evident in any of themecamylamine/nicotine (mec/nic) pretreatment groups. Further post-hoccomparisons indicated that the locomotor response to nicotine wassignificantly greater for the sal/nic pretreatment group when comparedto the other groups (p<0.05). The response to nicotine in the mec/nicpretreatment groups was not significantly different from those receivingno nicotine in the sal/sal pretreatment group (p<0.05), except in thecase of vertical activity, where all mec/nic groups had significantlyless activity then control.

Pretreatment with mecamylamine and both of its stereoisomers on nicotineexposure days, dose-dependently prevented the development of thesensitized locomotor responses to nicotine. Decreased vertical activityfollowing the test injection of nicotine alone (day 9) was found in ratsthat had received chronic mecamylamine/nicotine exposure relative tothose who had received chronic saline/saline exposure. This suggeststhat chronic exposure to mecamylamine actually reduce the locomotorresponse to nicotine to levels below that seen in the saline/salinegroup. Although both isomers of mecamylamine followed the same generalpattern, exo-R-mecamylamine was generally more effective at lower doses,particularly for center distance and vertical activity.

EXAMPLE 2

Recently it has been shown that some seizure disorders, including butnot limited to juvenile myoclonic epilepsy, autosomal dominant nocturnalfrontal lobe epilepsy and possibly inherited idiopathic epilepsy, aremediated through the α₄ and α₇ nicotine-binding receptors. Nicotine hasbeen shown to induce short periods of seizure activity in rats. Nicotinemay function in two distinct neuropharmacological ways to induceseizures: first, by activation of nAChRs involved with presynapticglutamate release and second, by causing inactivation of nAChRs involvedwith presynaptic gamma-amino butyric acid (GAVA) release. Okamoto et al.(Jpn J Pharmacol 59:449-55, 1992) showed that a single high dose ofmecamylamine (1.0 mg/kg) blocked nicotine-induced seizures in rats. Thepresent experiment evaluates the effect of exo-R-mecamylamine andexo-S-mecamylamine and the racemate in blocking nicotine-inducedseizures in rats. In addition, because α4β2 α7 nAChR antagonists(dihydro-β-erythroidine and methyllycaconitine, respectively) can alsoinduce seizures, a high dose of mecamylamine and its isomers were alsotested alone for potential seizure production.

Methods

Animals

Male Sprague-Dawley rats (n=96) weighing between 200 and 250 grams uponarrival were used for this study (Harlan Laboratories, Ind.). The ratswere housed two per cage, allowed one week to acclimate to animalfacility before testing, kept on a reverse lighting schedule (7:00-19:00lights off), and allowed free access to food and water. Testing occurredbetween 10:00 a.m. and 3:00 p.m. in a dimly lit room maintained at 22°C. The experimental procedures carried out in this study were incompliance with the Guide for the Care and Use of Laboratory Animals(National Research Council, 1996) and had the prior approval of theUniversity of South Florida Institutional Animal Care and Use Committee.

Apparatus

Observation of seizures and locomotor recordings were carried out inclear acrylic 41×41×30 cm test chambers inside Digiscan activitymonitors (Accuscan, Inc.). Each monitor employs two arrays of infraredphotocell beams (8×8 photocells, model RXYZCM-8) to detect severalparameters of the rat's movement both horizontally and vertically. Datawere collected in 5-min bins during testing.

Drugs

(−) Nicotine was purchased from Sigma Chemical Co., (St. Louis, Mo.) and(+/−)-Mecamylamine hydrochloride (Inversine®) and its stereoisomers wasobtained from Layton Bioscience, Inc., Sunnyvale, Calif.). All drugswere dissolved in physiological saline, and nicotine was adjusted to pHwith HCl to 7.40. All rats received subcutaneous (s.c.) injections in avolume of 1 ml/kg, and the drugs were prepared fresh each day. All dosesare expressed as the free base of the drug.

Mecamylamine Blockade of Nicotine-Induced Seizures

Ninety-six rats were randomly assigned to one of three conditions (n=32per condition): (±)-mecamylamine, exo-R-mecamylamine, orexo-S-mecamylamine. Rats in each condition were randomly assigned to oneof four treatment-drug groups (n=8 per group): 0.0 (saline), 0.1, 0.3,or 1.0 mg/kg mecamylamine. Two rats from each group, per condition, weretested at a time in a counter-balanced design. All testing for acondition was complete in a day. Rats were moved to the behaviorobservation room 30 minutes prior to testing. They received an injection(s.c.) in their home cages of (±)-mecamylamine, one of itsstereoisomers, or saline 15 minutes prior to nicotine injection of 3.6mg/kg (s.c.). After nicotine injection they were individually placeddirectly into a test chamber for 30 minutes of observation and locomotoractivity recording.

Two experimenters who were blind to the treatment groups of the ratsrecorded the following measures: number of seizures, latency to seize,and duration of seizure(s). In addition, during the 30-minute testingperiod, rats were rated once every 5 minutes on a severity scale, whichranged from 0-5. This scale was anchored to the following descriptors:0=no seizures, 1=myoclonic jerk, 2=forelimb clonus, 3=clonic/tonicseizure, 4=compete tonus (all four limbs), and 5=death. Other secondarymeasures were also recorded at 5-min intervals on scales from 0-10, with10 being the most severe, consisting of the following measures: severityof tremors, difficulty breathing, vocalization, activity level, andrighting.

Effects of Mecamylamine Alone at High Dose

Thirty-two rats were randomly assigned to 4 groups (n=8 per group)receiving saline or 10 mg/kg (s.c.) of either (±)-mecamylamine,exo-R-mecamylamine, and exo-S-mecamylamine. Immediately followinginjection, each rat was placed in the test chamber for 30 minutes ofobservation and locomotor activity recording. Two rats from each groupwere tested at one time in a counterbalanced design to control for ordereffects. All testing was completed in one day.

Statistical Analysis

Data was analyzed using a one-way analysis of variance followed byFishers least significance test for multiple comparisons. Statisticalsignificance was set at an alpha level of 0.05.

Results

Mecamylamine Blockade of Nicotine-Induced Seizures

Nicotine at 3.6 mg/kg produced 100% seizures in all the salinepretreatment groups (FIG. 6A). Mecamylamine and its stereoisomersprevented nicotine-induced seizures in a dose-dependent manner (FIG.6A). There was a significant overall effect for the measures of seizurelatency, duration, and seizure [F(11, 84)=37.24, 19.97, 30.17; p (all)0.0001, respectively]. Group comparisons on the seizure latency showedthat at 0.3 and 1.0 mg/kg (±)-mecamylamine and its stereoisomers hadsignificantly longer latency when compared to their saline controlgroups and the groups across the 0.1 mg/kg condition. Furthermore, ratsin the 0.1 mg/kg for both (±) and exo-S-mecamylamine groups hadsignificantly longer seizure latency than their saline comparisongroups. Also, at this dose the (±) mecamylamine showed longer seizurelatency when compared to the exo-R-mecamylamine group (FIG. 6B).

On the measures of duration and severity of seizure, rats in(±)-mecamylamine and in the stereoisomers at 0.3 and 1.0 mg/kg groupswere significantly different from their saline comparison groups and theother groups. However, in the 0.1 mg/kg treatment condition, the (±)-and exo-S-mecamylamine groups were significantly different from theirsaline comparison groups, where as rats in the exo-R-mecamylamine groupdid not differ from their saline comparison group (FIG. 6C).

Even though the rats in 0.1 mg/kg condition had more seizures than ratsin both the 0.3 and 1.0 mg/kg condition the severity of seizures weresignificantly less than that of their saline comparison groups (FIG.6D). No differences in secondary measures including locomotor activitywere found between racemic mecamylamine and its isomers in theseexperiments (data not shown).

Effects of Mecamylamine Alone at High Dose

There was no evidence for mecamylamine-induced seizures whenadministered at the high dose of 10 mg/kg (data not shown). However,significant differences in spontaneous locomotor activity were foundbetween isomers of mecamylamine when compared to saline control [F(3,28)=26; p=0.0001]. As represented in FIG. 7, all three mecamylaminecompounds reduced spontaneous locomotor activity as measured in totaldistance traveled, with the exo-S-mecamylamine isomer exhibitingsignigicantly less locomotor depressant effects than theexo-R-mecamylamine.

The present study demonstrated that mecamylamine and its optical isomersblock nicotine-induced seizures at low doses and that theexo-S-mecamylamine isomer appears to have inhibitory properties moresimilar to racemic mecamylamine than the exo-R-mecamylamine isomer. Forexample, fewer rats had nicotine-seizures in the racemic andexo-S-mecamylamine groups than did the exo-R-mecamylamine at the lowestdose (0.1 mg/kg) tested. Moreover, at this dose, only the racemic andexo-S-mecamylamine groups significantly increased seizure latency anddecreased the duration of seizures.

When tested alone at a high dose of 10 mg/kg, mecamylamine and itsstereoisomers failed to produce seizures. This finding is inconsistentwith a recent report of other nAChR antagonists causing seizures whengiven alone and does not support the hypothesis that nAChR inactivationis one way that nicotine causes seizures.

Another finding of the present study was exo-S-mecamylamine causedsignificantly less locomotor depressant effects than exo-R-mecamylamineat 10 mg/kg. This result is consistent with the finding thatexo-S-mecamylamine has less inhibitory effect at nAChR muscle receptorsthan exo-R-mecamylamine. Because muscle weakness is a common side effectassociated with mecamylamine treatment of children and adolescents, ourfindings, together with others', have important clinical implications.The fact that exo-S-mecamylamine has inhibitory properties more similarto racemic mecamylamine than to exo-R-mecamylamine, but with less motordepressant effects than either, suggests that exo-S-mecamylamine wouldbe a better medication for clinical development.

There are a few limitations of the present findings that deservediscussion. First, since seizure suppression was virtually complete with2 of the 3 doses, the doses chosen were too high to permit us toconclude that exo-S-mecamylamine is more potent than exo-R-mecamylamine.Moreover, in the absence of any pharmacokinetic data on the isomers ofmecamylamine, we cannot conclude that the differences found between theisomers in the present study are solely due to pharmacodynamicdifferences in their inhibitory properties at nAChrRs. Nevertheless, thedifferences that were found were consistent with what would be expectedbased on the available pharmacological evidence regarding thedifferences observed at the receptor level.

In summary, mecamylamine and its stereoisomers potently blocknicotine-induced seizures in rats with exo-S-mecamylamine displaying anoverall higher therapeutic index over exo-R-mecamylamine.

EXAMPLE 3

The aim of the study was to determine whether mecamylamine and itsstereoisomers have any effect on pressor responses and increases inplasma catecholamines in response to sympathetic nerve stimulation. Aspreviously established in the model of the pithed rat, modulation ofthese responses indicates changes in the release of adrenergicneurotransmitters and the responsiveness of the cardiovascular systemthereto.

Methods and Study Design

In the vagotomized, pithed and artificially respired rats (with oxygenmixed with air), the cardiovascular responses to test compounds measuredwere mean arterial blood pressure and heart rate; and the catecholamineresponses measured were plasma norepinephrine, epinephrine and dopamine.These variables were measured in rats at rest and after electricalstimulation of sympathetic outflow at 0.2 Hz, 0.8 Hz, and 2.2 Hz for aone-minute duration (50 V, 1 msec pulse), and before and afteradministration of vehicle or a drug. Catecholamine assays were performedby specific HPLC testing. Four groups of rats were studied: thosetreated with saline, exo-R-mecamylamine, (+/−)-mecamylamine andexo-S-mecamylamine by bolus injection of 0.1 mg/kg, 1.0 mg/kg, and 10mg/kg, administered intravenously. Statistical analysis were applied asappropriate.

Results—Cardiovascular Responses

In the vagotomized, pithed and artificially respired rats (with oxygenmixed with air), resting mean blood arterial pressure (MAP) wasapproximately 48 mmHg and heart rate was approximately 280 beats/min inall groups. In saline-treated rats, sympathetic nerve stimulationincreased MAP in a frequency-dependent manner by 4.2±1.0 mmHg at 0.2 Hz,16.1±4.9 mmHg at 0.8 Hz, and 27.1±7.1 mmHg (or up to around 80 mmHg MAP)at 2.2 Hz (all significantly different from baseline, p<0.05). In allother groups, rats treated with exo-R-mecamylamine, exo-S-mecamylamineand the racemate, the stimulation-induced increases in MAP were reducedat all frequencies but were completely abolished at 0.8 and 2.2 Hz(p<0.05 compared to saline-treated rats). Of all the drugs,exo-S-mecamylamine was the most potent because it shifted theMAP-stimulation frequency response curve significantly to the right ofthe one obtained in the presence of saline already at 0.1 mg/kg. Theother two forms, exo-R-mecamylamine and the racemate, significantlyright-shifted the pressure-stimulation curves at 1.0 and 10 mg/kg dosesof the drugs. In each of the drug-treated groups, changes in the MAPfrom baseline (δ MAP) during 0.8 Hz and 2.2 Hz were significantly lowerthan those of the saline-treated rats, and for the highest dose of thedrugs, stimulation at these frequencies actually caused the MAP to fallbelow baseline levels (p<0.05).

Heart rate responses to nerve stimulation were also similarly affectedby treatment with mecamylamine. At the highest dose of the drug,exo-R-mecamylamine and exo-S-mecamylamine and the racemate allsignificantly lowered the increases in heart rate (δ HR) at 2.2 Hz ascompared to those obtained in the saline-treated rats (p<0.05). As withthe pressor responses, stimulation-induced tachycardia was completelyblocked at 10 mg/kg of all forms of mecamylamine. There were nodifferences between the potencies of the three forms of mecamylamine inrespect to blocking the tachycardic response. The EC50s for thestimulation-induced pressor responses (δ MAPs) could not be determinedbecause the maximal pressor responses were not achieved for technicalreasons.

Catecholamine Responses

Plasma catecholamine (CA) levels—norepinephrine (NE), epinephrine (EPI),and dopamine (DA)—were measured by HPLC with an electrochemical detectorfollowing administration of doses of all forms of mecamylamine.

Resting plasma NE levels were between 100-200 pg/ml in all groups ofpithed rats and were not significantly different from each other. Thesympatholytic stimulation at 2.2 Hz evoked significant increases inplasma NE levels (increases from baseline and absolute values) in allmecamylamine-treatment groups. However, the stimulation-inducedincreases in plasma NE levels were significantly less in rats treatedwith exo-R-mecamylamine than in those in the saline treatment group(p<0.05).

Resting plasma EPI levels were between 50-60 pg/ml in all groups ofpithed rats and were not significantly different from each other. Thesympathetic stimulation at 2.2 Hz evoked increases in plasma EPI levels(from baseline and absolute values) in rats treated with saline andexo-R-mecamylamine (p<0.05). However, following the administration ofthe racemate and exo-S-mecamylamine, there was a significant decrease instimulation-induced plasma EPI responses at 2.2 Hz as compared to thoseof the saline-treated rats (p<0.05).

Surprising results were found by measuring plasma DA levels in thepithed rats. In control, saline-treated pithed rats, resting plasma DAwas found to be high, at around 9,000 pg/ml (8750±217 pg/ml), higherthan any other CA. Remarkably, all 3 isomers of mecamylamine markedlylowered basal plasma DA levels to around 500 pg/ml±104 (p<0.001). Inspite of markedly reduced baseline DA levels after the injections of thedrugs, the sympathetic stimulation at 2.2 Hz still caused significantincreases in plasma DA levels in saline-, exo-R-mecamylamine- and theracemate-treated rats, but not in rats treated with exo-S-mecamylamine.In both, R318- and R319-treated rats, stimulation-induced increases inplasma DA were significantly lower than in saline-treated rats.

The present study demonstrated that mecamylamine has profound effects oncardiovascular and CA responses to sympathetic nerve stimulation in vivoin pithed rats. All three forms of mecamylamine were effective inreducing pressor, tachycardic and CA responses to sympathetic nervestimulation but with some slight differences. All three forms hadsimilar effects on the pressor and tachycardic responses to nervestimulation, significantly lowering them at the higher frequencies ofstimulation, as compared to those of the control, vehicle-treated rats.Yet, of the three, exo-S-mecamylamine was the most potent in decreasingstimulation-induced pressor responses (already at the lowest dose of 0.1mg/kg). Exo-S-mecamylamine was also the only one that significantlydecreased stimulation-evoked plasma NE increases. As far as plasma EPIresponses are concerned, both exo-R-mecamylamine and the racematesignificantly decreased them as compared to the control responses. Andfinally, all three isomers lowered the elevated resting plasma DA levelsin the pithed rats but only the stereoisomers (not the racemate) reducedthe stimulation-induced DA responses. Overall, exo-S-mecamylamine wasthe most effective in reducing plasma CA as well as decreasingsympathetically-mediated cardiovascular responses.

These results suggest that mecamylamine may exert receptor- andnon-receptor mediated effects at the peripheral sympatheticneuro-effector junctions, through exo-R-mecamylamine andS-stereoisomers. The lowering effects of mecamylamine on thestimulation-evoked plasma NE and EPI levels, and on pressor andtachycardic responses, are consistent with its receptor-mediatedpresynaptic actions at both the peripheral sympathetic nerves and theadrenal medulla.

In conclusion, mecamylamine inhibits sympathetically mediated pressor,tachycardic and adrenergic (NE, EPT, DA) responses possibly by reducingthe release of those neurotransmitters at the peripheral neuroeffectorjunctions and the chromaffin cells of the adrenal medulla. However, themajor hypotensive effect of mecamylamine appears to be notstereoisomer-specific and may be related to reduction of highcirculating DA levels, present in the pithed rats.

EXAMPLE 4

This experiment evaluated the efficacy and potency of exo-S-mecamylamineon human α₃β₄, α₄β₂, α₃β₂, and α₇ receptors expressed in Xenopus oocytesand compared its activity to that of mecamylamine racemate. Voltagedependence and binding reversibility also were determined. Mature femaleXenopus laevis African loads were used as a source of oocytes. Afterlinearization and purification of cloned cDNAs, RNA transcripts wereprepared in vitro using the appropriate mMessage mMachine® kit fromAmbion Inc. (Austin Tex.). Harvested oocytes were treated withcollagenase (Worthington Biochemical Corporation, Freehold N.J.) for twohr at room temperature in calcium-free solution. Subsequently stage 5oocytes were isolated and injected with 50 nL each of a mixture of theappropriate subunit(s) cRNAs. Recordings were made about 1-7 days aftercRNA injection.

For electrophysiology, oocyte recordings were made with an oocyteamplifier (e.g., Warner Instruments, Hamden, Conn., No. OC-725C) andRC-8 recording chamber. Oocytes were placed in the recording chamberwith a total volume of about 0.6 ml and perfused at room temperature byfrog Ringer's solution (115 mM NaCl, 2.5 mM KCl, 10 mM HEPES pH 7.3, and1.8 mM CaCl₂) containing 1.mu.M atropine to inhibit potential muscarinicresponses. A Mariotte flask filled with Ringer's solution was used tomaintain a constant hydrostatic pressure for drug delivery and washes.Drugs were diluted in perfusion solution and loaded into a 2 ml loop atthe terminus of the perfusion line. A bypass of the drug-loading loopallowed bath solution to flow continuously while the drug loop wasloaded. The drug application was synchronized with data acquisition byusing a 2-way electronic valve. The rate of bath solution exchange anddrug application was preferably about 6 ml/min. Current electrodes werefilled with a solution containing 250 mMCsCl, 250 mM CsF and 100 mM EGTAand had resistances of 0.5-2 MΩ. Voltage electrodes were filed with 3MKCl and have resistances of 1-3 MΩ. Oocytes with resting membranepotentials more positive than −30 mV were not used.

Measurements of current responses to exo-S-mecamylamine application werestudied under two-electrode voltage clamp at a holding potential of −50mV unless otherwise noted. Holding currents immediately before agonistapplication were subtracted from measurements of the peak response toagonist. All drug applications were separated by at least a 5 min washperiod, longer if there is persisting drug effect. At the start ofrecording, all oocytes received two initial control applications ofacetylcholine (Ach). The second application of control ACh minimized theeffects of rundown that occasionally occur after an initial ACh-evokedresponse. The second application of ACh also was used to normalize forthe level of channel expression in each oocyte. To determine residualinhibitory effects, application of ACh with inhibitor or inhibitor alonewas followed by another application of ACh alone and compared to thepre-application control ACh response.

For each receptor subtype, a control ACh concentration was selected thatis sufficient to stimulate the receptors to a level representing areasonably high value of p_(open) at the peak of the response whileminimizing rundown from successive ACh applications. Such conditionswere adequate to achieve maximal inhibition. The control AChconcentration were 30 μm ACh for α4β2, 100 μM ACh for α3β4, 30 μM AChfor α3β2, 300 μM ACh for α7, and 3 μM ACh for α1β1δε. These correspondto the EC₃₀, EC₁₀, EC₁₅, EC₅₀, and EC₅₀, respectively, for thesereceptors.

For experiments assessing voltage-dependence of drug inhibition, oocyteswere initially voltage clamped at a holding potential of −40 mV or −90mV and 0.1 control application of ACh alone was delivered. A secondcontrol response was then obtained at the designated test potential. Theholding potential was kept at the designated voltage for theco-application of ACh with exo-S-mecamylamine. Residual inhibition wasevaluated with a subsequent application of ACh alone at the testpotential, after a 5-min wash period.

Inhibition of α₃β₄, α₄β₂, α₃β₂, and α₇ receptors was tested withexo-S-mecamylamine. For each of the β subunit-containing receptorsubtypes, there was a marked decrease in subsequent control response toACh when it was applied 5 min after exposure to exo-S-mecamylamine. Theresidual inhibition was greatest for β₂-containing receptors and leastfor α₇ receptors. Comparing the IC50 values, exo-S-mecamylamine was mostpotent at inhibiting α₃β4 receptors and least potent at inhibiting α₇receptors.

The selectivity of mecamylamines for neuronal nAChR was tested byexamining the effects of exo-S-mecamylamine on al α1β1δε mouse musclereceptors. This isomer had very little effect; and after a 5-min wash,inhibition of muscle receptors was fully reversed, unlike the inhibitionof β receptors. This decreased α1β1δε receptor effect indicates thatexo-S-mecamylamine may cause less tiredness or weakness, which has beenreported in smoking cessation studies and in a Tourette's study.

The effects of exo-S-mecamylamine also were tested on oocytescoexpressing NMDA receptor subunits NR1 and NR2b. NR1 is ubiquitous inthe brain and produces robust functional responses when coexpressed withthe NR2b subunit and activated by glutamate and the coagonist glycine.NR2b in vivo is selectively present in the forebrain with high levels ofexpression in the cerebral cortex and hippocampus, as well as theseptum, caudate putamen and olfactory bulb, making the combination ofNR2b and NR1 relevant for both cognitive and motor functions in the CNS.When exo-S-mecamylamine was applied to NR1/NR2b preparations at aconcentration of 100 μM, it produced a transient inhibition to theco-application of 10 μM glutamate+10 μM glycine, which was reversibleafter a 5-min wash. These studies support the specific central nicotiniceffect of exo-S-mecamylamine.

The recovery time course for nicotine receptors is important to note.Recovery time course experiments were performed at 5-min intervals andextended to about one-half hour. An initial inhibition of greater than50% was obtained with the co-application of 10 μM exo-S-mecamylamine andACh at the control concentration, and then followed the responserecovery with control ACh applications every 5 min. For β₂ receptors,recovery from inhibition seemed to follow simple exponential kinetics.For α₃β₂ receptors, exo-S-mecamylamine had a time constant of recoveryof about 33 min, which was similar to the time constant of recovery ofthis isomer at α₄β₂ receptors. Exo-S-mecamylamine off-loaded from somereceptors slower than exo-R-mecamylamine which implies that a lowerdosage or less frequent dosage may be used with the former. This couldreduce toxicity.

In contrast to the β₂-containing receptors, recovery of α₃β₄ receptorsdid not follow simple exponential kinetics. There appeared to be a fastphase lasting an average of 19 minutes. However, after that, there wasno further recovery. This suggests that mecamylamine may exert twoqualitatively different forms of inhibition on these receptors.Mecamylamine did not appear to compete with ACh on α₄β₂ or α₄β₄receptors. The relative amount of inhibition produced by a fixedconcentration of mecamylamine was relatively constant over a wide rangeof ACh concentrations. In the absence of ACh, mecamylamine atconcentrations of 10 nM-100 μM were applied to receptors, but no agonistactivity was observed.

The voltage dependence of the exo-S-mecamylamine activity was determinedby co-applying ACh and isomer. First, cells were held at either −40 mVor 90 mV and tested for response to control concentrations of ACh. Aftera 5-min wash, ACh and the isomer were applied. This permitted theevaluation of voltage at the onset of inhibition and at recovery.Mecamylamine concentrations were 10 μM for α₇ receptors, 5 μM for α₄β₂and α₃β₂ receptors, and 1 μM for 60₃β₄ receptors. There was significantvoltage dependence for the α₄β₂ and α₃β₄ receptors. Exo-S-mecamylaminealso had significantly different responses at α₃β₂ and α₇ receptors.These results indicate that the binding site for mecamylamine may bedeep enough into the membrane's electric field to slow the dissociationof mecamylamine when the cell is hyperpolarized.

EXAMPLE 5

Cocaine use is an increasingly common problem in the United States, withestimates of lifetime use prevalence rates at 2.5% and currentprevalence rates of cocaine abuse or dependence rates of about 1%.(Regier et al., 1990). There are no known effective treatments, asidefrom expensive, personnel-intensive supervision and counseling programs.

Many schizophrenic and depressed patients also have a high incidence ofcocaine use; rates are estimated to be 40-50% (Shaner et al., 1995). Ofcocaine abusers, it has been estimated that as many as 75% also aredependent on nicotine (Budney et al., 1993), as opposed to a smokingrate of 22% in controls.

Animal results with regard to cocaine, nicotine and mecamylamine havebeen equivocal. On the one hand, cocaine and its analogues bind calfbrain with modest affinity to the non-competitive ion channel site onthe high-affinity nAChR, the site of action of mecamylamine(Lerner-Marmarosh N, Carroll F I and Abood L G, Life Sciences56(3):67-70, 1995). Cocaine was moderately effective in antagonizing thebehavioral effects of nicotine. However, in mice, systemicadministration of mecamylamine (1 mg/kg) and dihydro-beta-erythroidine(2 mg/kg)—nicotinic antagonists—and atropine (2 mg/kg)—a muscarinicantagonist—were ineffective against psychostimulant-induced stereotypyin naive animals. All three drugs were ineffective against either theinduction or expression of cocaine sensitization. Karler, Brain Res.1996 (July 1) 725(2):192-8. Spealman and Goldberg tested the effects ofmecamylamine on the schedule-controlled behavior by intravenousinjections of nicotine and cocaine in squirrel monkeys. J Pharm ExpTherap 223:403-06, 1982. Administering mecamylamine before theexperimental session caused responding maintained by nicotine, but notby cocaine, to fall within saline-control levels.

This example utilizes HEK293 cells expressing cDNA for a variety ofhuman neurotransmitters to determine a compound's affinity therewith andits ability to inhibit interactions with cocaine. The HEK 293 withinserts of hDAT (dopamine transporter), hSERT (serotonin transporter) orhNET (norepinephrine transporter) were grown to 80% confluence on 150 mmdiameter tissue culture dishes and serve as the tissue source. Cellmembranes were prepared as follows. Medium was poured off the plate, andthe plate was washed with 10 ml of calcium- and magnesium-freephosphate-buffered saline. Lysis buffer (10 ml; 2 mM HEPES with 1 mMEDTA) was added. After 10 min, cells were scraped from plates, pouredinto centrifuge tubes, and centrifuged at 20,000×g for 20 min. Thesupernatant fluid was removed, and the pellet resuspended in 12-32 milof 0.32 M sucrose using a Polytron centrifuge setting of 7 for 10 sec.The resuspension volume depends on the density of binding sites within acell line and was chosen to reflect binding of 10% or less of the totalradioactivity. Exo-S-mecamylamine was weighed and made up into a 10 mMstock solution in DMSO. Subsequent dilutions were made in assay buffer,achieving a final concentration of 0.1%.

For the assay, each tube was prepared with 50 μl of membrane preparation(about 10-15 μg of protein), 25 μl of ex-S-mecamylamine or buffer(Krebs-HEPES, pH 7.4; 122 mM NaCl, 2.5 mM CaCl₂, 1.2 mM MgSO4, 10 μmpargyline, 100 μM tropolone, 0.2% glucose and 0.02% ascorbic acid,buffered with 25 mM HEPES), 25 μl of [¹²⁵I]RTI-55 (40-80 pM finalconcentration) and additional buffer sufficient to bring up the finalvolume to 250 μl. Membranes were preincubated with exo-S-mecamylaminefor 10 min prior to the addition of the [¹²⁵I]RTI-55. The assay tubeswere incubated at 25° C. for 90 min. Binding was terminated byfiltration over GF/C filters using a Tomtec 96-well cell harvester.Filters were washed for six seconds with ice-cold saline. Scintillationfluid was added to each square and radioactivity remaining on the filterwas determined using a Wallac μ- or β-plate reader. Specific binding wasdefined as the difference in binding observed in the presence andabsence of 5 μM mazindol (HEK-hDAT and HEK-hNET) or 5 μM imipramine(HEK-hSERT). Two or three independent competition experiments wereconducted with duplicate determinations. GraphPAD Prism statisticalprogram was used to analyze the resulting data, with IC50 valuesconverted to Ki values using the Cheng-Prusoff equation.

The affinity of exo-S-mecamylamine for each type of binding site waslower than the affinity of cocaine for the same site.

EXAMPLE 6

The effect of exo-S-mecamylamine in cocaine addiction treatment wasassessed in a locomotor depression test. The study was conducted using40 Digiscan activity-testing chambers (40.5×40.5×30.5 cm) housed in setsof two, within sound-attenuating chambers. A panel of infrared beams (16beams) and corresponding photodetectors were located in the horizontaldirection along the sides of each activity chamber. A 7.5-W incandescentlight above each chamber provided dim illumination. Fans provided an80-dB ambient noise level within the chamber. Separate groups of 8non-habituated male Swiss-Webster mice (Hsd:ND4, aged 2-3 months) wereinjected via the intraperitoneal (ip) route with either vehicle (0.9%saline) or exo-S-mecamylamine (0.3, 1.3, or 10 mg/kg doses), 20 minutesprior to locomotor activity testing. Just prior to placement in theapparatus, all mice received a saline injection. In all studies,horizontal activity (interruption of photocell beams) was measured forone hour within 10-min periods. Testing was conducted with one mouse peractivity chamber.

First, saline and four doses of exo-S-mecamylamine were tested alone for60 minutes. The exo-S-mecamylamine dose producing one half of themaximal depressant activity (where maximal depression is 0 counts in 30minutes) was calculated as 8.5 mg/kg. Stimulant effects of 1 and 3 mg/kgdoses were evident during the last 30 minutes of testing. Then thecocaine interaction study was performed as a function of time andexo-S-mecamylamine dose. Twenty minutes following injection of saline ormecamylamine, saline or 20 mg/kg cocaine ip was administered, and micewere placed in the Digiscan apparatus for one hour. Cocaine's effect isbelieved to be maximal at 30 minutes. At that time point, saline/cocainewas producing the highest locomotion; whereas, the administration ofsaline/saline and 10 mg/kg exo-S-macamylamine/cocaine were bothsignificantly different from the result of cocaine alone. Interesting,the latter two test groups diverged by the end of the hour: Thelocomotion of the saline/saline group steadily declined to 60 minutes;whereas, the 10 mg/kg group's locomotion did not decrease further. Thereported attenuated locomotor activity index (AD₅₀) was 3.3 mg/kg forexo-S-mecamylamine, compared to 6.2 mg/kg for exo-R-mecamylamine.

Other Uses

Recent reports suggest that nicotine reduces the symptoms ofschizophrenia (Adler L E et al, Am J Psychiatry 150:1856-1861, 1993),Attention Deficit Hyperactivity Disorder (ADHD) (Levin E D et al,Psychopharmacology 123:55-62, 1995) and depression (Salin-Pascual R J etal, Psychopharmacology 121(4):476-479, 1995). While it is generallybelieved that nAChr activation is responsible for nicotine's therapeuticactions in these “nicotine-responsive” disorders (Decker M W et al, LifeSci, 56:545-570, 1995), it is clear that, like many other drugs,nicotine has complex neuropharmacological effects. Thus, many peoplewith such nicotine-responsive disorders, could be helped with a nAChrblocker which has been disclosed herein with the example ofmecamylamine, a nAChr blocker, which reduced the symptoms in thenicotine responsive disorders, TS and ADHD.

Schizophrenia, a psychiatric disorder theorized to involvehyperdopaminergic tone, is most often treated with neuroleptics; butthere is now speculation that it is a nicotine-responsive disorder. Forexample, surveys of schizophrenic patients have demonstrated rates ofsmoking between 74% and 92%, compared to 35% to 54% for all psychiatricpatients and 30%-35% for the general population. It has been speculatedthat cigarette smoking may improve underlying psychopathology byenhancing concentration and reducing anxiety from hyperarousal(Gopalaswamy A K, Morgan R, Br J Psychiatry, 149:523, 1986). Inaddition, nicotine may have some role to play in reducing the cognitivedeficits associated with schizophrenia and neuroleptic treatment.Cigarette smoking has been found to normalize sensory gating deficits inschizophrenic patients (Adler L E et al, Am J Psychiatry 150:1856-1861,1993) and a recent study found that transdermal nicotine reversed someof the adverse cognitive effects of standard antipsychotic medicationand improved cognitive performance in general for schizophrenic patients(Levin E D et al, Psychopharmacology 123:55-63, 1996). If as we nowhypothesize that nicotine administration may actually have a similareffect as a nAChr blocker, then it is possible that a nAChr blocker suchas a mecamylamine isomer would also reverse the adverse cognitiveeffects of the antipsychotic medication and improve cognitiveperformance in schizophrenic patients. Moreover, since nicotinepotentiates the therapeutic effects of neuroleptics in TS (McConville BJ et al, Biological Psychiatry 31: 832-840, 1992), the use ofmecamylamine as an adjunct to neuroleptics in “neuroleptic-responsive”disorders such as schizophrenia and Huntington's chorea, can allow forreducing the neuroleptic dose, thereby reducing the side effects of theneuroleptic without reducing its therapeutic effects. Nevertheless,based on the above experiences of mecamylamine in Tourette's, bipolarpatients and patients with schizophrenia-like symptoms, cocaine abusersare also likely to benefit from treatment with mecamylamine and othernicotine antagonists.

The treatment of viral infections, particularly herpes I and II, hasbeen successfully undertaken with ganglionic blocking agentstetraethylammonium or hexamethonium (U.S. Pat. No. 5,686,448). Becauseexo-S-mecamylamine has ganglionic blocking action, it can be expected tobe similarly efficacious against viral infections.

Mecamylamine has been shown to reduce organophosphate poisoningtoxicity. For example, when rats were dosed with 8 mg/kg of DFP (anorganophosphate), all died within 5 hours. However, 3 of 4 ratsreceiving mecamylamine at 30 mg/kg and the lethal dose of DFP survivedbeyond 5 hours. Rats receiving a combination of mecamylamine and 2-PAMand then the lethal dose of DFP all survived. It would be beneficial tolower the dose of mecamylamine by administering only the effectiveisomer.

Alpha₄, but not alpha₃ and alpha₇, nicotinic acetylcholine receptorsubunits are lost from the temporal cortex in Alzheimer's disease.Neuronal nicotinic acetylcholine receptors labelled with tritiatedagonists are reduced in the cerebral cortex in Alzheimer's disease (AD).Autopsy tissue from the temporal cortex of 14 AD cases and 15age-matched control subjects were compared using immunoblotting withantibodies against recombinant peptides specific for alpha₃, alpha₄, andalpha₇ subunits, in conjunction with [³H]epibatidine binding. Antibodiesto alpha₃, alpha₄, and alpha₇ produced one major band on western blotsat 59, 51, and 57 kDa, respectively. [³H]Epibatidine binding andalpha₄-like immunoreactivity (using antibodies against the extracellulardomain and cytoplasmic loop of the alpha₄ subunit) were reduced in ADcases compared with control subjects (p<0.02) and with a subgroup ofcontrol subjects (n=9) who did not smoke prior to death (p<0.05) for theformer two parameters. [³H]Epibatidine binding and cytoplasmicalpha₄-like immunoreactivity were significantly elevated in a subgroupof control subjects (n=4) who had smoked prior to death (p<0.05). Therewere no significant changes in alpha₃- or alpha₇-like immunoreactivityassociated with AD or tobacco use. The selective involvement of alpha₄has implications for understanding the role of nicotinic receptors in ADand potential therapeutic targets (Martin-Ruiz C M et al. Neurochem 1999October; 73(4):1635-40).

Cancer also may be treated with mecamylamines. Lung cancer demonstratesa strong etiologic association with smoking. Of the two most commonhistologic lung cancer types, small cell carcinoma (SCLC) is foundalmost exclusively in smokers, whereas peripheral adenocarcinoma (PAC)also develops in a significant number of nonsmokers.N′-Nitrosonornicotine (NNN) and4(methylnitrosamino)-1-(3-pyridyl)-1-buta-none (NNK), nicotine-derivednitrosamines, are potent lung carcinogens contained in tobacco products(Schuller & Orloff, 1998).

Using cell lines derived from human small cell lung carcinoma andpulmonary adenocarcinoma with the nicotinic receptor selective ligandsalpha-bungarotoxin (alpha-BTX) and epibatidine (EB) in receptor bindingand cell proliferation assays, it was reported that SCLC expressedneuronal nicotinic receptors with high affinity to alpha-BTX, whereasPAC cells expressed nicotinic receptors with high affinity to EB(Schuller & Orloff, Biochem Pharmacol 55(9):1377-84, 1998). NNK boundwith high affinity to alpha-BTX-sensitive nAChRs in SCLC cells, whileNNN bound with high affinity to EB sensitive nAChRs in PAC cells. Theaffinity of each nitrosamine to these receptors was several orders ofmagnitude greater than that of nicotine. NNK stimulated theproliferation of SCLC cells via this mechanism. These findings suggestthat NNK may contribute to the genesis of SCLC in smokers via chronicstimulation of the alpha BTX-sensitive nAChR-subtype expressed in thesecells, which is most likely the alpha₇ containing subunit (Schuller etal., 2000). The alpha₇ nicotinic acetylcholine receptor and itsassociated mitogenic signal transduction pathway is emerging as animportant growth regulator of pulmonary neuroendocrine cells and smallcell lung carcinoma and may be critically involved in the development ofneoplastic and non-neoplastic pulmonary diseases.

Mecamylamine, especially the exo-S-mecamylamine, would be expected tointerrupt nicotine and NNK stimulated the proliferation of SCLC cells insmokers and thus should be useful for treating SCLC.

The foregoing description and examples are intended only to illustrate,not limit, the disclosed invention.

All of the patents, patent applications and references referred to aboveare incorporated herein by reference.

We claim:
 1. An oral pharmaceutical composition comprising: an effectiveamount of exo-S-mecamylamine or pharmaceutically acceptable salt thereofsubstantially free of exo-R-mecamylamine or a pharmaceuticallyacceptable salt thereof; one or more pharmaceutically acceptablecarriers; and a pharmaceutical adjuvant, wherein the oral pharmaceuticalcomposition has a higher overall therapeutic index than the same amountof exo-R-mecamylamine substantially free of exo-S-mecamylamine.
 2. Theoral pharmaceutical composition of claim 1, wherein the pharmaceuticalcomposition is a unit dosage form.
 3. The oral pharmaceuticalcomposition of claim 2, wherein the unit dosage form is selected fromthe group consisting of a tablet, capsule, soft gelatin capsule, hardgelatin capsule, powder, lozenge, gum, emulsion, suspension, syrup, andsolution.
 4. The oral pharmaceutical composition of claim 1, wherein thepharmaceutical composition is formulated to provide rapid, sustained, ordelayed release of the exo-S-mecamylamine or a pharmaceuticallyacceptable salt thereof.
 5. The oral pharmaceutical composition of claim1, wherein the effective amount of exo-S-mecamylamine orpharmaceutically acceptable salt thereof is from about 0.001 mg/kg toabout 6 mg/kg per day.
 6. The oral pharmaceutical composition of claim1, wherein the effective amount of exo-S-mecamylamine orpharmaceutically acceptable salt thereof is from about 0.01 mg/kg toabout 1.5 mg/kg per day.